Digital Image Authentication Self-recovery

With the coming of information era and the rapid developing of Internet, multimedia information is used widely and deeply. In the meantime, people have paid much attention to the issues of multimedia information security. In the face of the coming of multimedia information, people always wonder if it is authentic, if it is altered by anyone else or if we should accept them or reject them. All kinds of questions like this affect our normal work and life.Multimedia authentication techniques are the important ways to look after the security of the multimedia. They are usually designed based on two kinds of tools: digital signature or watermarking. Digital signature is a non-repudiatible, encrypted version of the message digest extracted from the data. Watermarking techniques consider multimedia data as a communication channel transmitting owner identification or content integrity information. Given an objective for multimedia authentication to reject the crop-and-replacement process and accept content-preserving manipulations, traditional digital signature or watermarking methods cannot be directly applied.In this thesis, we first induce and sum up the general theories to multimedia authentication, from which we get some universality conclusions. On the base of these conclusions, we present anovel digital signature-A Recoverable Active Digital Signature Method for Digital Image:RADS, according to the characteristics of multimedia information like digital image and the requirements of digital image authentication. Then we show a lot of experimental results and practical examples to prove RADS is an effective and practical digital signature way. The results show that RADS can not only reject all kinds of illegal un-acceptable manipulations and accept any kind of legal acceptable ones, but also exactly detect the location of altered areas of image and approximately recover its corrupted pixels modified by any kind of manipulation. RADS has so many practical values that it is a new digital signature worth being popularized. In order to present the feasibility of RADS in detail, in this paper, we also design and develop a RADS based digital image authentication prototype system which can show the whole process how to use RADS to authenticate an image perfectly.